Questions covered in this guide
An acronym leaves important choices open
Carlisle organizes its resources by membrane family and attachment system, including adhered and mechanically fastened options. A quote containing only TPO, PVC, or EPDM has not identified all the choices represented in that manufacturer’s documentation.
Ask for a roof assembly description
Request the exact membrane product and thickness, the proposed attachment approach, and a list of the layers beneath it. Ask the contractor to identify what stays from the existing roof and what is removed. This is a request for their design, not an instruction to select a particular method. For a home with a small low-slope addition, ask whether the proposed system documentation actually applies to that substrate and roof configuration.
Make the documents comparable
Create three columns headed proposed assembly, supporting document, and unresolved question. Enter membrane, attachment, insulation, cover board if proposed, edges, and penetrations as separate rows. Have the roofer connect each row to the project scope. Leave a row empty when information is missing rather than filling it from an unrelated online detail. Keep different bidders’ descriptions intact until each explains its own assembly; combining pieces yourself can create a specification nobody has agreed to install.
Compare the finished result
Request a written explanation for material or attachment differences before comparing totals. Include the same retained-roof assumptions and closeout documents in each proposal. Ask what future repair information you should keep for the selected membrane. The national roof calculator does not validate a single-ply design or price all these layers. Use it as early planning context, then rely on a project-specific specification and itemized proposal for your decision.
Putting it into practice
The homeowner requests a complete named assembly and traces each layer to the contractor’s documents. This prevents a membrane acronym from hiding differences in attachment and retained materials between proposals.
Sources and supported claims
Carlisle lists separate EPDM, TPO, and PVC system resources for estimators.
Source ↗ · national · Checked 2026-10-12
Carlisle separates adhered and mechanically fastened roof system documentation in its estimator resources.
Source ↗ · national · Checked 2026-10-12